June will be a busy month, it seems: Senate Majority Leader Harry Reid (D-Nev.) has said that he wants to wrap up debate and vote on the bill by the July 4 recess.

Compared to legislative failures in 2007 and 2010, the odds that this immigration bill passes look better, but are still not guaranteed. Pro-reform advocates were encouraged by the large number of senators on both sides of the aisle who voted yes. The original test vote received 82 aye votes when 60 were needed.

Earlier on Tuesday, President Obama threw his full weight behind the bill during a speech at the White House. He prodded both Republicans and Democrats to support the measure, calling it "the best chance we've had in years to address this problem."

"To truly deal with this issue, Congress needs to act," he said. "And that moment is now."

But challenges lie ahead that could make its road to passage more difficult in the Senate. Many Republicans who voted to proceed to debate on Tuesday said they are uncommitted to supporting the Gang of Eight's immigration plan on a final vote.

"Today's vote isn't a final judgment of their product as much as it is a recognition of the problem," Senate Minority Leader Mitch McConnell (R-Ky.) said on the floor on Tuesday.

With 54 seats, Democrats will need to attract at least a handful of Republican senators to acquire 60 votes, the number needed to avoid a filibuster of the final vote of the bill.
The bill's authors have hoped to attract more than 60 votes to urge the House to act.

Beyond the four Republicans on the Gang of Eight, the group that drafted the legislation, only one GOP senator has pledged her support so far: Kelly Ayotte (N.H.)

An amendment by Sen. John Cornyn (R-Texas) has gained traction among GOP senators who are on the fence on the legislation. The proposal would implement stricter border security benchmarks before immigrants who are granted temporary legal status can apply for legal permanent residence.

McConnell, who voted to proceed, told reporters on Tuesday that he wants to see changes to the bill's border security language and government benefits clauses before he can support it.

"Sen. Cornyn, in my view, has got the key amendment to put us in a position where we could actually look at the American people with a straight face and say, 'We are going to secure the border,'" he said.

But top Democrats have come out against the amendment, saying it could further impede undocumented immigrants from obtaining permanent status after the a 10-year wait that's already included in the Senate bill.

Reid called the measure a "poison pill" during a Univision interview this weekend. In his speech, Obama did not reference the amendment, but he called the current bill the "the biggest commitment to border security in our nation's history."

"Now, this bill isn't perfect. It's a compromise," Obama added. 'And going forward, nobody is going to get everything that they want -- not Democrats, not Republicans, not me. But this is a bill that's largely consistent with the principles that I and the people on this stage have laid out for common-sense reform."